Interpretive Summary: Root-feeding larvae are important economical pests of crops and require control measures. However, the use of conventional pesticides has raised concerns over potential contamination to the environment. Consequently, biological control agents, which are considered safer and offer environmentally-friendly advantages, have been promoted as an alternative approach. Entomopathogenic nematodes when harbored within desiccated cadavers are more capable as a control measure of root-feeding larvae. In this study, a crop seed planter was modified to determine whether irregular-shaped, fragile and nematode-infected desiccated cadavers could be effectively delivered into the soil at a desired rate and depth as the seed planter traveled continuously along a row. Laboratory and field tests demonstrated that, although feasible, to improve accuracy of the seed planter, metering plates must be specifically designed for this system to discharge desiccated cadavers at different rates.

Technical Abstract:
Pentomopathogenic nematodes may be more capable of controlling soil pests when they are harbored by desiccated cadavers. A small-scale system was developed from a modified crop seed planter to effectively deliver desiccated nematode-infected cadavers into the soil. The system mainly consists of a metering unit, an air pressure source, a cadaver scraper, a custom-designed cadaver container, tension adjustment devices, double disk soil opener, a discharge tube, a packer wheel, and a press/drive wheel. The metering unit intermittently discharges a cadaver to the discharge tube at a constant rate. The double disk opener creates a narrow 7.5 cm deep slot for the placement of the discharged cadavers. The press wheel then covers the cadavers with loose and somewhat moist soil. The spring tension device and the press wheel control the slot depth. The number of cells on the metering plate controls the cadaver delivery rate regardless of the travel speed. The metering unit with modified double bean plates has delivery accuracy between 79 and 94% at 500 Pa air pressure. A slower travel speed and fewer cells on the metering plate improved the accuracy of delivery. When the travel speed was 4.8 km/h or slower, the desiccated cadaver delivery system performed satisfactorily in both laboratory and field tests, and delivered the cadavers at a rate of 1.6, 3.3 or 6.6 cadavers per meter length in the soil.